Remove libcxxrt from the manifest.

We moved away from this project a while ago.

Bug: 17451546
Remove external/grub.

This project is horribly out of date, and is no longer used.
No longer need bootable/diskinstaller.

This was only used by the vbox target, which is now dead.
Remove platform/external/sil-fonts

BUG:17508191
Change-Id: I7bc7dc244e5f5839630395bef4104a102428a667
Remove platform/external/hyphenation and platform/external/libxslt

Change-Id: I1b42f5417f9225c56c8f8a4bef30ff519112d398
Remove platform/frameworks/opt/mailcommon

Change-Id: I1e7d2554a46f3999c04b151abc5c0a9318cd714a
Merge branch 'master' of https://github.com/android/platform_manifest into HEAD

Change-Id: I9d1bcc3b1bcead492de1901312482d1a0c36cde2